code: def state_key(self):
      return self._generate_state_key(unique=self._unique)
  
imports: import contextlib
  import logging
  from unittest import mock
  from unittest.mock import Mock
  import pytest
  import torch
  from lightning.fabric.utilities.imports import _PYTHON_GREATER_EQUAL_3_8_0, _PYTHON_GREATER_EQUAL_3_10_0
  from lightning.pytorch import Callback, LightningModule, Trainer
  from lightning.pytorch.callbacks import EarlyStopping, GradientAccumulationScheduler, LearningRateMonitor, ModelCheckpoint, ModelSummary, ProgressBar, TQDMProgressBar
  from lightning.pytorch.callbacks.batch_size_finder import BatchSizeFinder
  from lightning.pytorch.demos.boring_classes import BoringModel
  from lightning.pytorch.trainer.connectors.callback_connector import _CallbackConnector
label_desc: Use image node_id 2 for calling the StatefulCallback1 obj's underlying member method code with example usage: obj.state_key() and returns: self